Typically, a solenoid valve comprises an armature movable between a first and second position. The extremes of these first and second positions are often defined by mechanical stops. Armatures can be moved in one direction by an electro-magnetic force generated by a solenoid and moved in the opposite direction by a return or bias spring. When the armature impacts a stop and because of its mass it tends to bounce. Therefore, to reduce bounce and its detrimental effects, many parameters may be changed, one being the mass of the armature. Each bounce of the armature causes the valve element to meter a small uncontrolled amount of fuel into the engine, to the detriment of emissions. As can be appreciated, the leakage of fuel into the engine will also result in very unfavorable fuel economy. Furthermore, the bounce of the armature affects the operation of a fuel injector by causing excessive wear in the valve seat area.
The armature is typically a solid structure with drilled passages or "fuel holes" that allow fluid to pass through the armature to the valve. For armatures where the flow rate is high, these drilled passages can become quite large and negatively impact magnetic performance due to insufficient magnetic path area. Unfortunately, increasing the magnetic path area to correct for the drilled holes increases the mass of the armature, which may negatively impact the dynamic characteristics of the armature.
It is seen then that it would be desirable to have a solution to the problems created by drilled passages in armature pieces.